The present invention relates generally to magnetic field sensors and specifically to a configuration for a coupled film magnetic transducer. It is well known that a long, thin strip of magnetoresistive film, e.g., NiFe, can be set in a single domain state such that the magnetization is parallel to the long dimension of the strip. Once the strip has been set in a single domain state, the resistance of the strip versus an external magnetic field can be represented by a bell shaped curve as shown in FIG. 1. To obtain a linear output, the strip is typically subjected to an external bias field that places its resistance in the middle of one of the linear portions of the bell shaped curve. It has been shown that adjacent thin films magnetoresistive material separated by an interlayer material undergo magnetostatic coupling.
In certain magnetic field sensing applications, the space available for sensing devices is extremely limited and there is a need for miniaturized magnetic field sensors. Further in certain applications there is a need to be able to adjust or vary the response characteristics of the sensing device while it is in use. An example is the use of magnetic field sensing devices within a known magnetic field to establish the location of another device to which the sensor device is attached. A coupled film magnetic field sensor inherently offers certain advantages relative to miniaturization.
Thus a need exists for a coupled film miniaturized magnetic sensor in which the response characteristics may be varied while in use.